Coupling circuit independent of frequency



Sept 5, 1939. H, B'AHRING 2,172,150

COUPLING CIRCUIT INDEPENDENT OF FREQUENCY Filed Sept. 16, 1956 gwucnko o alkozuu Patented Sept. 5, 1939 UNllED STATES PATENT OFFIQE COUPLING CIRCUIT INDEPENDENT F FREQUENCY Application September 16, 1936, Serial No. 101,176 In Germany October 15, 1935 2 Claims.

The invention relates to electrical coupling elements and deals more particularly with an inductive coupling of circuit elements in a manner independent of the frequency.

In coupling loudspeakers for example or in coupling deflecting coils of cathode oscillographs or television transmitting and receiving tubes it is important that all of the frequencies be transmitted in the same manner in order to avoid distortions which might arise by neighboring or more closely tuned frequency ranges.

In accordance with the invention the time constants of the two current paths are made equal to each other and hence a coupling is produced which is independent of the frequency.

The subject matter of the invention is more clearly explained by means of an embodiment In the drawing:

Fig. 1 is a basic circuit diagram for an inductive coupling.

Fig. 2 is a representation of the direct current blocking coupling of an inductive consumption device, e. g. a loudspeaker or a deflecting coil of a cathode ray tube located in the final stage of an amplifier.

Fig. 3 is a push pull amplifier circuit.

Fig. 4 is a representation of a choke condenser coupling for an amplifier tube at its preliminary stage.

In Fig. 1 the current branching is indicated by resistance R1 and the inductivity L1 in one branch, and the resistance R2 as well as the inductance L2 in the other branch. The requirement is that in the case of all frequencies the current i2 in the second branch is proportional to the current 2 preceding said branching. This condition is fulfilled if EiFz that is if the time constants of the two current branches are equal.

The circuit of Fig. 2 which contains the final tube ,1 of an amplifier and attachment terminals 2, 3 for an inductive consumption device, is therefore provided with a variable resistance R1 which fulfills the above recited conditions. Insofar as the time constant of the inductance L1 is greater than that of the consumption device, the desired coupling may be produced by varying R1 alone. If the time constant of L1 is smaller than that of the consumption device the above mentioned conditions can be fulfilled by inserting the resistance B: into the consumption device branch.

In the push-pull circuit of Fig. 3 in which two final tubes 4 and 5 are provided, the coupling is likewise produced by correspondingly proportioning the resistances R1R1'. In this case the condenser may be eliminated since the anodes of the tubes are at the same potential.

Maintenance of the rule propounded in accordance with the invention is of especial importance in the case of television devices since in that case extraordinarily large frequencies ranges are encountered. Thus it is possible so to adaptingly proportion the inductivity L1 provided in a relaxation device, by inserting a resistance R1 at the consumption device, 1. e. in this case the deflecting coil, that the time constants are equal to each other and thus obtain a coupling for the zig-zag current of the relaxation circuit which is free from distortion.

Fig. 4 shows a choke coupling independent of frequency and provided with equalizable current branches. A power tube 6 is for example connected to the last tube I of a capacity-resistance coupled amplifier. The inductive coupling, contrasted with the capacity resistance coupling is of greater significance since:

1. By using chokes instead of resistances the direct current votage drop at the anode resistance is greatly reduced so that a lower anode voltage source suflices,

2. In the power tube 6 the grid also becomes strongly heated owing to back radiation from the strongly heated anode so that electrons issue therefrom. In ordinary capacity resistance coupling the current thus engendered causes a positive voltage drop to occur at the grid cathode resistance, which is impressed on the grid voltage provided and which compensates the latter to a large extent so that the tube becomes positively biased and amplifies in a distorted manner. With a choke coupling the thermal grid emission current so produced does not act in a disturbing manner.

I claim:

1. In combination, a source of oscillations of a predetermined wave shape, deflecting means for a cathode ray device and means for coupling said deflecting means to said source of oscillations comprising a plurality of sections of substantially the same time constant with one of said sections including said deflecting means.

2. In combination, a plurality of electron discharge devices connected in push-pull arrangement and including an output circuit having predetermined time constants, and a load connected to said output circuit having a like time constant.

HERBERT BAHRING. 

